Flow control valve for exhaust gas recirculation system

ABSTRACT

A flow control valve is provided for use in an exhaust gas recirculation system of an internal combustion engine, whereby a constant flow of the recirculating gas may be maintained. The valve comprises a first and second valve chamber separated by a flow orifice with a valve body being provided to effect opening and closing of the flow orifice. Exhaust gas entering the first chamber passes through the orifice into the second chamber and to the engine intake system. Located upon one side of the valve body is a diaphragm responsive to exhaust gas pressure in the first chamber and connected to move the valve body in response thereto. A pressure compensating piston located in the second valve chamber has the intake manifold pressure applied thereto and is configured to balance the effects of said intake manifold pressure upon the valve body. Throttling means in the form of a throttling orifice define the entrance of the exhaust gases into said first valve chamber and spring means apply, to the side of said diaphragm opposite the side to which the exhaust gas pressure is applied, a force tending to counterbalance an opposing force slightly higher the the force of atmospheric pressure acting upon the diaphragm. Atmospheric pressure is also applied to the pressure compensating piston in a direction opposite to the direction in which intake manifold pressure is applied.

United States Patent 1 Goto et al.

[ 51 Dec. 30, 1975 [54] FLOW CONTROL VALVE FOR EXHAUST GAS RECIRCULATION SYSTEM [75] Inventors: Kenji Goto; Ryozo Mitsui, both of Susono, Japan [73] Assignee: Toyota Jidosha Kogyo Kabushiki Kaisha, Japan 22 Filed: Sept. 25, 1973 211 Appl. No.: 400,674

Primary Examiner-Douglas Hart Attorney, Agent, or Firm-Toren, McGeady and Stanger [57] ABSTRACT A flow control valve is provided for use in an exhaust gas recirculation system of an internal combustion engine, whereby a constant flow of the recirculating gas may be maintained. The valve comprises a first and second valve chamber separated by a flow orifice with a valve body being provided to effect opening and closing of the flow orifice. Exhaust gas entering the first chamber passes through the orifice into the second chamber and to the engine intake system. Located upon one side of the valve body is a diaphragm responsive to exhaust gas pressure in the first chamber and connected to move the valve body in response thereto. A pressure compensating piston located in the second valve chamber has the intake manifold pressure applied thereto and is configured to balance the effects of said intake manifold pressure upon the valve body. Throttling means in the form of a throttling orifice define the entrance of the exhaust gases into said first valve chamber and spring means apply, to the side of said diaphragm opposite the side to which the exhaust gas pressure is applied, a force tending to counterbalance an opposing force slightly higher the the force of atmospheric pressure acting upon the diaphragm. Atmospheric pressure is also applied to the pressure compensating piston in a direction opposite to the direction in which intake manifold pressure is applied.

9 Claims, 2 Drawing Figures FLOW CONTROL VALVE FOR EXHAUST GAS RECIRCULATION SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a flow control valve for use in an exhaust gas recirculation system for an automobile internal combustion engine. More particularly, the invention relates to a system whereby control of the flow rate of the recirculating exhaust gas may be maintained at a relatively constant level and applied at a point in the engine intake system downstream from the carburetor throttle valve.

2. Description of the Prior Art Recirculation of automotive engine exhaust gases is intended for the purpose of reducing nitrogen oxides in the automobile emissions. Generally, it is desired that the amount of the exhaust gas which is recirculated be maintained at a constant rate relative to the rate of the intake of the engine regardless of the operating condition of the engine. For this reason, prior art arrangements usually provide for part of the exhaust gas to be applied into the intake system of the engine at a point upstream of the throttle valve of the carburetor. Such recirculated exhaust is delivered through a throttling device and through a regulator valve. However, inasmuch as the exhaust gases must pass through the carburetor, there will arise problems of corrosion of carburetor parts, sticking and clogging of parts as well as formation of frost at low temperatures. One solution for these problems has, in prior systems, involved the application of the recirculated exhaust gas flow to a point downstream of the throttle valve of the carburetor. In such a case, however, the intake manifold pressure in the intake system of the engine will be increased inversely to the intake of fuel into the engine. Accordingly, it becomes necessary to control the amount of recirculated exhaust gasin accordance with the negative intake pressure in order to maintain such recirculating gas flow at a constant rate relative to the flow rate of the engine intake. In the past, several types of variable throttle mechanisms have been proposed in attempts to overcome the aforementioned problems but none of these have proved satisfactory from the point of view of their practical utilization in engine systems.

Accordingly, it is an object of the present invention to provide a flow control system for recirculating exhaust gases in an internal combustion engine, whereby the recirculated exhaust may be applied at a point downstream of the throttle valve of the carburetor, with the flow rate of the recirculated exhaust being effectively controlled so that it will remain constant relative to the flow rate of the engine intake flow.

SUMMARY OF THE INVENTION Briefly, the present invention may be described as a flow control system for recirculating exhaust gases in an internal combustion engine including intake means for providing a combustible mixture to said engine and exhaust means for removing exhaust gases therefrom. The system of the invention comprises means defining a first valve chamber and a second valve chamber, means defining a flow orifice located between said first and said second chambers, a valve body mounted for movement to open and close said flow orifice, means for delivering exhaust gases from the exhaust means of the engine to the first valve chamber, throttle means provided in said exhaust gas delivering means and located approximately midway therein to have said first valve chamber on the downstream side thereof, means communicating the second valve chamber with the engine intake means, a diaphragm connected with the valve body and mounted to have pressure in the first valve chamber applied to one side thereof to control opening and closing of the flow orifice in accordance with said first valve chamber pressure, and a pressure compensating piston connected to the valve body and located to have pressure in the second valve chamber applied thereto, the piston being configured to counteract the action of the pressure from within the engine intake means upon the valve body. Accordingly, the pressure in the first valve chamber is maintained at a constant value approximating atmospheric pressure and operates to control the flow rate of the recirculating exhaust gases.

Additionally, spring means acting upon the diaphragm to bias the valve body in the direction of closing of the flow orifice are also provided. The spring means are selected to apply a biasing force to the diaphragm on one side thereof which will overcome a force slightly higher than the force of atmospheric pressure applied to the opposite side of the diaphragm. Furthermore, atmospheric pressure is applied to the pressure compensating piston ina direction opposite to the direction in which the pressure in the second valve chamber is applied thereto. In the operation of the present invention, the aforementioned problems of previously known systems may be overcome by controlling the pressure in the first valve chamber so that it may be maintained at a substantially constant value approximating atmospheric pressure.

DETAILED DESCRIPTION OF THE DRAWINGS A better understanding of the present invention may be had by reference to the following detailed description of a preferred embodiment thereof, taken in connection with the accompanying drawings wherein:

FIG. 1 is a schematic diagram showing an overall exhaust gas recirculating system, utilizing the valve of the present invention;

FIG. 2 is a sectional view of the recirculating gas flow control valve in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, there is shown an internal combustion engine 1 having an intake system including an intake pipe 2 and an exhaust system including an exhaust pipe 3. A portion of the exhaust emitted from the exhaust pipe 3 is directed back into the intake pipe 2 through an exhaust recirculation pipe 4. A flow control valve 5, structured in accordance with the present invention, is disposed within the exhaust recirculation pipe 4 halfway between the exhaust 3 and the intake 2. The exhaust from the exhaust pipe 3 enters the valve 5 through an exhaust inlet port 6 and is emitted therefrom for delivery to the intake 2 through an outlet port 7.

The structure of the valve 5 of the present invention is shown in more detail in FIG. 2. The valve 5 is provided with a valve casing 8 divided into a first pressure chamber 9 and a second pressure chamber 10, said chambers having formed therebetween a flow passage 11 defined by a wall extending between the two chambers. The first or upper chamber 9 communicates with the exhaust pipe 3 through the exhaust inlet port 6 and the second or lower chamber 10 communicates with the intake pipe 2 through the exhaust outlet 7. Throttling means in the form of a throttling orifice 12 are provided at a suitable location between the exhaust pipe 3 and the upper chamber 9, with the orifice 12 in FIG. 2 being shown at the entrance to the chamber 9. A valve body 13 is disposed within the chamber 9 to open and close the flow passage 11.

Provided above the casing 8 is a diaphragm chamber 14 which is sectioned into an upper chamber 16 and a lower chamber 17 by a diaphragm 15 which is connected to the .valve body 13 through a valve rod 18. The valve rod 18 extends through an opening 19 defined in the wall separating the chamber 17 from the chamber 9. The opening 19 is formed of a size large enough not only to enable the valve rod 18 to freely move therein but also to place the chamber 9 in flow communication with the chamber 17 so that the pressure in the chamber 9 will be applied through the chamber 17 to the underside of the diaphragm 15. A spring 20 located within the chamber 16 urges the diaphragm l downwardly in the direction of closing of the orifice 11 by the valve body 13. The spring force of the spring 20 is selected so that when the pressure in the chamber 9, and consequently in the chamber 17, reaches a level slightly higher than atmospheric pressure, such as, for example, when such pressure becomes slightly higher than the exhaust gas pressure during idling, the spring load of the spring 20 will be equal to the upward force acting upon the diaphragm 15. Y

A pressure compensating piston 21 adapted to counteract the force of the intake manifold pressure acting on the underside of the valve body 13 is mounted at the lower end of the valve rod 18 with the piston 21 being slidably engaged within a cylinder portion 22 provided at the bottom of the valve casing 8. The internal pressure in the chamber below the valve body 13 acts upon the upper side of the piston 21 and atmospheric pressure applied through an aperture 23 formed in the bottom of the valve casing 8 acts upon the underside of the piston 21. The piston 21 is configured to have a pressure area which is selected such that the force produced due to the negative intake pressure upon the valve body 13 will be cancelled. Accordingly, the force produced by pressure upon the upperside of the piston 21 will be equal in magnitude but opposite in direction to the negative pressure acting upon the valve body 13. Accordingly, the action of the valve rod 18 and of the valve body 13 will be controlled only by the force of pressure acting upon the diaphragm and by the pressure of the spring 20. I

A labyrinth packing 24 is provided between the pressure compensating piston 21 and the cylinder portion 22 in order that air entering between the skirt of the, piston 21 and the valve casing defining the cylinder portion 22 will be controlled to a small amount so that such air will not produce adverse influence upon the engine. The pressure compensating piston 21 is arranged to be smoothly slidable relative to the cylinder portion 22 and also to be resistant to wear'and heat. Additionally, there is also provided a protective filter 25 which is adapted to prevent small particles in the exhaust gas from clogging the opening 19 which communicates the chamber 9 above the valve body with the chamber 17 below the diaphragm, thereby to ensure that smooth movement of the valve rod 18 within the opening 19 will always occur.

The chamber 16 located above the diaphragm 15 is arranged in flow communication either with, for example, the discharge side of an air pump 27 or with an atmospheric release pipe 28, as shown in FIG. 1, through an aperture 26. A solenoid valve 29 operates to switch communication between the chamber 16 and either the air pump 27 or the atmospheric release pipe 28. The solenoid valve 29 is designed so that in the case of forcibly checking recirculation of the exhaust gases under certain operating conditions, such as, when the engine speed is above a certain set level or when the temperature is below a certain set level, high pressure on the discharge side of the air pump 27 will be applied to the chamber 16 to close the valve body 13. The air pump 27 is provided for supplyingsecondary air which, as is well known to those skilled in the art, is used for exhaust purification and is usually communicated with the atmospheric release pipe 28 through aperture 26.

In the flow control valve 5 as described above, the chamber 9 will'always be controlled at a pressure approximating atmospheric pressure. When the engine is in operation, the negative pressure of the intake pipe 2 will act upon the underside of the valve body 13, but the force produced by such negative pressure is cancelled by the pressure compensation piston 21. Accordingly, only the pressure of the exhaust gas acting upon the diaphragm 15 and the pressure of the spring 20 will operate to control the valve rod 18, so that the amount of force lifting the valve body 13 and hence controlling the flow rate of exhaust gases into the intake pipe 2, will be determined in relation with the exhaust gas pressure acting upon the diaphragm 15 and the pressure of the spring 20. Accordingly, if the pressure of the exhaust gases introduced from the exhaust inlet port 6 is small, the pressure acting upon the diaphragm 15 will also be small and hence the lifting force upon the valve 13 will be lessened by the pressure of the spring 20 thereby to throttle the flow passage 11. If

exhaust gas pressure is increased, pressure in the chamber 9 will also be increased and the lifting force upon the valve body 13 will be stabilized at a position where the pressure acting upon the diaphragm 15 will be balanced by the pressure applied by the spring 20. If the pressure of the exhaust gas introducedthrough the exhaust inlet 6 is further increased, pressure in the chamber 9 willalso be increased accordingly to increase the pressure acting upon the diaphragm 15, thereby increasing the lifting force acting upon the valve body 13 against the force of the spring 20. In this manner, the amount of. exhaust gas passing through the flow orifice 11 will be increased, and as the flow rate is thus raised, pressure in the chamber 9 will be lowered and .the .forces controlling movement of'the valve-body 13 will be stabilized at a position where pressure in the chamber 9 is balanced with pressure applied. by the spring 20.-

Accordingly, exhaust flow is controlled in accordance with the pressure acting upon the diaphragm 15, Le, the pressure in the chamber 9, which remains balanced against the pressure of the spring 20, which has been set to approximate atmospheric pressure, regardless of the rise or fall of the engine exhaust gas pressure. In such a case, if the spring constant of the spring 20 is selected to be sufficiently small to render inconsequential the variation of load caused by variation of lift with respect to the setting load within the scope of the valve body lift, it is possible to maintain pressure in the chamher 9 substantially constant.

In the flow control valve, as previously described herein, when an exhaust gas pressure P is applied to the exhaust inlet port 6, exhaust gas flows into the chamber 9 through the throttling orifice 12, but pressure in the chamber 9 will be maintained at a reduced level Py. In such a case, assuming that atmospheric pressure is Pa, then P Pa so that the quantity of recirculated exhaust gas G is represented by the fol lowing formula:

On the other hand, a relationship as indicated below exists between the exhaust pressure P and the engine take flow Hence, the relationship G 0: G is established. Accordingly, if the chamber 9 above the valve body 13 is controlled so that a constant pressure is maintained approximating atmospheric pressure, the rate of the exhaust gas recirculation flow relative to the rate of flow of the engine intake will be controlled to remain substantially constant regardless of engine operation conditions.

In the embodiment described, a throttle 30 is provided in the aperture 26 in the chamber 16 above the diaphragm for preventing pulsating motion of the diaphragm 15. For the same reason, the area of the space 19 communicating chamber 9 with the chamber 17 is selected to be within a range which will avoid impairment of the responsiveness of the valve body. Additionally, if thermal conditions permit, a bellows mechanism may be used in the section of the valve which is comprised of the pressure compensation piston 21 and the cylinder 22 to prevent entry of air.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

l. A flow control system for circulating exhaust gases in an engine, including intake means for providing a combustible mixture to said engine and exhaust means for removing exhaust gases therefrom, said system comprising, in combination, means defining a first valve chamber and a second valve chamber, means defining a flow orifice between said first and second chambers, a valve body mounted for movement to open and close said flow orifice, means for delivering exhaust gases from said exhaust means to said first valve chamber, throttling means provided in said exhaust gas delivering means located to have said first valve chamber on the downstream side thereof, means communicating said second valve chamber with said intake means, a diaphragm connected with said valve body and mounted to have pressure in said first valve chamber applied to one side thereof to control opening and closing of said flow orifice in accordance with said first valve chamber pressure, an air pump for delivering secondary air to said engine exhaust means, means for selectively applying the pressure of said secondary air to the side of said diaphragm opposite the side upon which said first valve chamber pressure is applied, and a pressure compensating piston affixed to said valve body and located to have pressure in said second valve chamber applied thereto, said piston being configured to generate a force upon said valve body resulting from application to said piston of said second valve chamber pressure which substantially equally counteracts the action of pressure from said intake means upon said valve body.

2. A system according to claim 1, including spring means acting upon said diaphragm to bias said valve body in the direction of closing of said flow orifice.

3. A system according to claim 2 wherein said spring means is located to act upon said diaphragm on a side thereof opposite the side upon which pressure in said first valve chamber is applied thereto.

4. A system according to claim 1 wherein said throttling means comprises a throttling orifice located at a point midway between said engine exhaust means and said engine intake means.

5. A system according to claim 1, including means for applying atmospheric pressure to said pressure compensating piston, said atmospheric pressure being applied thereto in a direction opposite to the direction in which said pressure in said second valve chamber is applied thereto.

6. A system according to claim 2, wherein said spring means is selected to create a biasing force which equivalently counteracts a force Slightly higher than the force of atmospheric pressure acting against the side of said diaphragm opposite said spring means.

7. A system according to claim 1, including means for selectively applying atmospheric pressure to the side of said diaphragm opposite the side upon which said first valve chamber pressure is applied.

8. A system according to claim 7, including switch means for selectively applying either said secondary air pressure or said atmospheric pressure to said side of said diaphragm.

9. A system according to claim 1, including an operating rod interconnecting said diaphragm and said valve body, means defining an operating orifice through which said operating rod extends, said operating orifice being sized to permit movement of said operating rod therein and passage therethrough of pressure from said first valve chamber applied to said diaphragm, and a protective filter located in said first valve chamber between said operating orifice. and said exhaust gas delivery means to prevent impurities in said exhaust gases from passing therethrough and clogging said operating orifice. 

1. A flow control system for circulating exhaust gases in an engine, including intake means for providing a combustible mixture to said engine and exhaust means for removing exhaust gases therefrom, said system comprising, in combination, means defining a first valve chamber and a second valve chamber, means defining a flow orifice between said first and second chambers, a valve body mounted for movement to open and close said flow orifice, means for delivering exhaust gases from said exhaust means to said first valve chamber, throttling means provided in said exhaust gas delivering means located to have said first valve chamber on the downstream side thereof, means communicating said second valve chamber with said intake means, a diaphragm connected with said valve body and mounted to have pressure in said first valve chamber applied to one side thereof to control opening and closing of said flow orifice in accordance with said first valve chamber pressure, an air pump for delivering secondary air to said engine exhaust means, means for selectively applying the pressure of said secondary air to the side of said diaphragm opposite the side upon which said first valve chamber pressure is applied, and a pressure compensating piston affixed to said valve body and located to have pressure in said second valve chamber applied thereto, said piston being configured to generate a force upon said valve body resulting from application to said piston of said second valve chamber pressure which substantially equally counteracts the action of pressure from said intake means upon said valve body.
 2. A system according to claim 1, including spring means acting upon said diaphragm to bias said valve body in the direction of closing of said flow orifice.
 3. A system according to claim 2 wherein said spring means is located to act upon said diaphragm on a side thereof opposite the side upon which pressure in said first valve chamber is applied thereto.
 4. A system according to claim 1 wherein said throttling means comprises a throttling orifice located at a point midway between said engine exhaust means and said engine intake means.
 5. A system according to claim 1, including means for applying atmospheric pRessure to said pressure compensating piston, said atmospheric pressure being applied thereto in a direction opposite to the direction in which said pressure in said second valve chamber is applied thereto.
 6. A system according to claim 2, wherein said spring means is selected to create a biasing force which equivalently counteracts a force slightly higher than the force of atmospheric pressure acting against the side of said diaphragm opposite said spring means.
 7. A system according to claim 1, including means for selectively applying atmospheric pressure to the side of said diaphragm opposite the side upon which said first valve chamber pressure is applied.
 8. A system according to claim 7, including switch means for selectively applying either said secondary air pressure or said atmospheric pressure to said side of said diaphragm.
 9. A system according to claim 1, including an operating rod interconnecting said diaphragm and said valve body, means defining an operating orifice through which said operating rod extends, said operating orifice being sized to permit movement of said operating rod therein and passage therethrough of pressure from said first valve chamber applied to said diaphragm, and a protective filter located in said first valve chamber between said operating orifice and said exhaust gas delivery means to prevent impurities in said exhaust gases from passing therethrough and clogging said operating orifice. 